.\"	$OpenBSD: MD5.3,v 1.9 2024/05/26 09:54:16 tb Exp $
.\"	OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400
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.\" Richard Levitte <levitte@openssl.org>.
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.Dd $Mdocdate: May 26 2024 $
.Dt MD5 3
.Os
.Sh NAME
.Nm MD4 ,
.Nm MD5 ,
.Nm MD4_Init ,
.Nm MD4_Update ,
.Nm MD4_Final ,
.Nm MD5_Init ,
.Nm MD5_Update ,
.Nm MD5_Final
.Nd MD4 and MD5 hash functions
.Sh SYNOPSIS
.In openssl/md4.h
.Ft unsigned char *
.Fo MD4
.Fa "const unsigned char *d"
.Fa "unsigned long n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo MD4_Init
.Fa "MD4_CTX *c"
.Fc
.Ft int
.Fo MD4_Update
.Fa "MD4_CTX *c"
.Fa "const void *data"
.Fa "unsigned long len"
.Fc
.Ft int
.Fo MD4_Final
.Fa "unsigned char *md"
.Fa "MD4_CTX *c"
.Fc
.In openssl/md5.h
.Ft unsigned char *
.Fo MD5
.Fa "const unsigned char *d"
.Fa "unsigned long n"
.Fa "unsigned char *md"
.Fc
.Ft int
.Fo MD5_Init
.Fa "MD5_CTX *c"
.Fc
.Ft int
.Fo MD5_Update
.Fa "MD5_CTX *c"
.Fa "const void *data"
.Fa "unsigned long len"
.Fc
.Ft int
.Fo MD5_Final
.Fa "unsigned char *md"
.Fa "MD5_CTX *c"
.Fc
.Sh DESCRIPTION
MD4 and MD5 are cryptographic hash functions with a 128-bit
output.
.Pp
.Fn MD4
and
.Fn MD5
compute the MD4 and MD5 message digest of the
.Fa n
bytes at
.Fa d
and place it in
.Fa md ,
which must have space for
.Dv MD4_DIGEST_LENGTH No == Dv MD5_DIGEST_LENGTH No == 16
bytes of output.
.Pp
The following functions may be used if the message is not completely
stored in memory:
.Pp
.Fn MD5_Init
initializes a
.Vt MD5_CTX
structure.
.Pp
.Fn MD5_Update
can be called repeatedly with chunks of the message to be hashed
.Pq Fa len No bytes at Fa data .
.Pp
.Fn MD5_Final
places the message digest in
.Fa md ,
which must have space for
.Dv MD5_DIGEST_LENGTH No == 16
bytes of output, and erases the
.Vt MD5_CTX .
.Pp
.Fn MD4_Init ,
.Fn MD4_Update ,
and
.Fn MD4_Final
are analogous using an
.Vt MD4_CTX
structure.
.Pp
Applications should use the higher level functions
.Xr EVP_DigestInit 3
etc. instead of calling these hash functions directly.
.Sh RETURN VALUES
.Fn MD4
and
.Fn MD5
return pointers to the hash value.
.Pp
.Fn MD4_Init ,
.Fn MD4_Update ,
.Fn MD4_Final ,
.Fn MD5_Init ,
.Fn MD5_Update ,
and
.Fn MD5_Final
return 1 for success or 0 otherwise.
.Sh SEE ALSO
.Xr EVP_DigestInit 3
.Sh STANDARDS
RFC 1320, RFC 1321
.Sh HISTORY
.Fn MD5 ,
.Fn MD5_Init ,
.Fn MD5_Update ,
and
.Fn MD5_Final
appeared in SSLeay 0.4 or earlier and have been available since
.Ox 2.4 .
.Pp
.Fn MD4 ,
.Fn MD4_Init ,
.Fn MD4_Update ,
and
.Fn MD4_Final
first appeared in OpenSSL 0.9.6 and have been available since
.Ox 2.9 .
.Sh CAVEATS
Other implementations allow
.Fa md
in
.Fn MD4
and
.Fn MD5
to be
.Dv NULL
and return a static array, which is not thread safe.
